The present invention relates to a machine for tying together elongated objects with the aid of a wire tie, and particularly for lashing or tying together reinforcement rods or bars, electric cables or the like, wherein the machine includes two jaws which can be swung relative to one another and which are provided with curved, wire-guiding surfaces that are caused to surround or straddle the objects to be tied together to enable the wire to be advanced along the wire-guide surfaces such as to form the wire into a wire loop that essentially surrounds the objects, by virtue of opening the jaws subsequent to advancing the wire and then moving the jaws for re-closure of said jaws on opposite sides of the objects, wherein the machine includes a supportive device adapted to support against said objects, and wherein the jaws are movable towards and away from the objects in relation to said supportive device in forming said wire loop around said objects.
Traditionally, reinforcement rods, or bars, are tied to form a tied mesh reinforcement with the aid of simple, manually-operated tools, which is a very time-consuming task and therewith a costly process, and also entails work which can result quite easily in strain-induced injuries to the workmen involved. This is because when tying reinforcement rods to produce a tied mesh reinforcement for concrete slabs, concrete floors or the like, with the aid of earlier known machines, it is necessary for the workman to remain in a stooped position for prolonged periods of time, therewith placing the spine of the workman under great bodily stress and strain as well as other parts of the workman's body.
The reinforcement rods are normally tied with the aid of pliers or twisters, by means of which the ends of a generally U-shaped wire tie positioned manually around the reinforcing rods at their mutual points of intersection are twisted or wound together so as to provide a stable tie. Conventional tying of reinforcement rods also creates accident hazards, particularly when working on roofs, bridges and similar structures, owing to the stooped position in which the workman is forced to work, such hazardous working positions also placing the workman at the risk of falling.
Machines which enable reinforcement rods to be tied mechanically with the workman in an upright working position have also been earlier proposed.
One such machine is described in WO 87/02313, although one drawback with this machine is that it is difficult for the workman to decide in which position the machine shall be held when closing the jaws for the advancement of a wire. A similar problem occurs when the machine is later to be lifted, subsequent to opening the jaws for renewed closure of the jaws on the upper side of the reinforcement rods. If the machine is lifted too high, the wire will be drawn out of the jaws and therewith prevent the wire ends being twisted together. The use of a machine of this kind is also tiring, because the workman must constantly carry the full weight of the machine.
It is true that a machine taught by WO 84/04772 includes a support element which is intended to coact with the reinforcement rods when advancing the wire through the jaws, but it is necessary to lift the machine manually prior to twisting the wire-ends together and remove the support from the reinforcement rods since said support would otherwise be tied firmly to the rods by said wire. It is also difficult with this machine for the workman to decide the height to which the machine shall be lifted prior to commencing twisting of the wire-ends. If the machine is lifted too high, the ends of the wire will be drawn out of the jaws and therefore cannot be twisted together. Furthermore, a great deal of precision is required with such a machine in order to achieve firm lashing of the reinforcement rods, since it is necessary to constantly hold the machine at precisely the correct level or height above the rods and because this height must be adapted during the rod lashing operation. This machine is also heavy to work with, because the full weight of the machine must be supported by the workman during the moment of tying the rods together.
DE-A1-4 008 222 teaches a machine having a supportive element which includes a rotational body for gripping and entraining the wire ends as the body rotates. In this case, the wire-ends are not twisted together by the jaws, but require the presence of additional means. This machine is also sensitive to dirt and to careless handling, both of which are liable to damage the bearing surfaces on the front parts of the jaws.
WO 92/06260 teaches a machine which includes an internal supportive element. The wire tie cannot be stretched with the aid of the jaws of this machine, and neither can the wire-ends be twisted together with the aid of said jaws. Separate rotating elements are therefore required to this end.